isn't time a quantifier for that which exists in any given state within a given space?
time is irrelevant if there is nothing to measure? and once that thing has come and gone you have your measure of time?
space = 3 dimensions. L W D or X Y Z
time = how long ^ these exist
thus space-time is the (to modern science) best available definition of a thing.
as for the theory of gravity affecting an object in space, there is no answer given science can't give a perfect explanition of what gravity is.. a push a pull another force such as the strong and weak atomic force that exists in a grandeur scale (one we can see and measure easily).
the better question is what do you think gravity is? a push, a pull, a static force with a static metric or a dynamic force with an ever varying metric (one that only appears static to us at our familiar scales).
i'm sure with a better understanding of the innards of the atom we'll get the answer, such as strings are gyroscopic in nature and they impart local fields on the matter they make up.
or you have silly theories like gravity is only a property of certain forms of matter..
[OH ^

.. by that i meant silly theories in general .. yikes retrospect is like new specs the world is so clear and flawed viewed thru them]
or gravity is instead an exotic for of osmotic radiation (larger objects take energy from close by objects).. in the same vain you could say atmospheric pressure is gravity and that the magnetic core theory is hogwash...
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don't call me skinny! i'm just ...

<<< ... aerodynamic!
its in my initials, an anagram.. seriously!